Vehicle traffic flow may be controlled or impeded by a variety of conditions. For example, traffic lights control the ability of vehicles to move through an intersection. In some cases, how a particular condition affects the traffic flow may depend on a status for the traffic condition. Thus, for example, if a traffic light is red for one direction, traffic flow in that direction is impeded in that direction for a certain period of time. Drivers often become aware of the status of a particular traffic flow device only after viewing the device, which limits the ability of drivers to be aware of traffic conditions and to adjust their routes accordingly. Particularly in the case of emergency vehicles, this can substantially interfere with the ability of vehicles to reach a destination in a timely manner. Also, in conditions of limited visibility, such as rainstorms or fog, these problems can become even more pronounced.